Murine monoclonal antibodies specific for HLA-D antigens precipitate a set of internally labeled polypeptides from human lymphoblastoid B cell lines which on two-dimensional protein electrophoresis give a pattern which is strikingly similar to most, but not all, of the polypeptide gene products of the murine I-A and I-E/C subregions of the mouse I region. Additional monoclonal antibodiees will be produceed to generate a set capable of precipitating all of the human counterparts of the presently detectable murine Ia antigens expresssed on B lymphocytes. Classification of HLA-D polypeptides as analogous to gene products of the I-A or I-E/C subregions will be determined using mouse allonantisera which cross-react with human lymphoblastoid B cell lines. Thse monoclonal HLA-D antibodies will be used to determine the two-dimensional protein electrophoresis patterns of all the available HLA-D homozygous typing cell lines, HLA-D heterozygotes, and HLA-D blanks in an effort to develop a two-dimensional electrophoretic genotypic reference library. Once this aim has been accomplished, HLA-D genotyping by two-dimensional protein electrophoresis will be carried out in Caucasian and Japaneese patients with juvenile onset diabetes mellitus, and in Caucasian patients with ankylosing spondylitis, Reiter's disease, rheumatoid arthritis, and systemic lupus erythematosus. These latter studies will be carried out in an attempt to identify one or a combination of HLA-D gene products which show a higher association (perhaps approaching 100%) with a particular disease, than has been detectable by HLA-D typing with homzygous typing cells in the mixed lymphocyte culture reaction or with HLA-DR sera.